The Wonderful Benefits Of Water Fluoridation
Why you should be grateful for the fluoride in your water
There are many amazing public health advancements from the 20th century. Antibiotics, vaccination, sewerage systems - all things we now take for granted that have been developed so that you and I can have a healthier life than people who came before us.
Among the most fascinating improvements in public health is water fluoridation. This is the practice of adding a tiny amount of the naturally-occurring fluoride into the water supply for places where there isn’t much fluorine in the environment. Many high-income nations put some amount of fluorine in public drinking water, although in some countries it’s instead added to other things like salt.
The practice of water fluoridation has always been very controversial. Fluoride, like pretty much all substances, is highly toxic in very substantial doses. In addition, there have long been concerns that even tiny amounts of fluoride can cause ill health, especially in children.
Fortunately, the evidence is quite clear that water fluoridation is a massive public health win. In the extremely low quantities that we add to drinking water, fluoride prevents dental decay and has no noticeable negative health effects.
Let’s look at the science.
The Story
I can’t write about water fluoridation without talking about the story behind the practice, because it’s just a really cool example of pragmatic public health policy in action.
In the early 1900s, a bunch of people around the world started noticing that there were areas where people had these weird brown stains on their teeth. Perhaps the most famous of these was the dentist Frederick Mackay, who noticed at the very start of the century that people in Colorado appeared to have these odd brown stains on their teeth. He quickly coined the name Colorado Brown Stain, and in 1909 managed to present his findings to the Colorado State Dental Association.
Unfortunately, 1909 was only a short time after the 1886 discovery of fluorine, and so Mackay and his colleagues did not immediately connect the two. They did, however note two fascinating facts - firstly, that there appeared to be some connection to the water supply, and secondly that children with these brown teeth were also surprisingly resistant to dental decay.
This led to a succession of studies which looked into the question of what could be causing this phenomenon. By the 1930s, studies in the UK and US had found a common denominator in areas with high rates of brown teeth - elevated levels of the element fluorine in the water. Further epidemiological investigation showed that you could add a tiny amount of fluorine into drinking water which would have the same benefits for teeth without causing the unsightly brown stains that characterized the initial findings.
And thus, we have water fluoridation. At this point in the 21st century, we have strong and consistent evidence that adding a tiny bit of fluorine into your diet - whether that’s from water, or salt, or just toothpaste - has enormous benefits for teeth at the population level.
So why is the practice controversial?
Health Concerns
There are two main health worries about adding fluoride to drinking water - IQ and thyroid function. While both have some reasonable basis, they tend to be blown entirely out of proportion by conspiracy theorists who claim that fluoride is a mind-control device and that adding it to water is a government scheme.
The IQ question came from a simple finding - in areas of high naturally-occurring fluoride, people tend to have slightly lower IQs than in regions with no naturally-occurring fluoride.
The thing is, areas with high levels of naturally-occurring fluoride are also different in many ways to areas without much natural fluoride in the water. They tend to be rural regions who source water directly from unfiltered streams which pass over fluorine-rich sediment, rather than cities where water is highly filtered before getting to a tap.
The first issue here is that natural fluorine tends to be at a much higher concentration than the stuff we use in tap water - in the systematic review I referenced above, these areas had about 4-5x as much fluoride as the average in public health programs (4mg/L vs 0.3-1mg/L).
The other problem is that areas with high naturally-occurring levels of fluoride are also very different to places with no fluoride in lots of ways. They are lower income, have worse schooling, and are in many ways less healthy than people who live in places where there isn’t much natural fluoride in the water.
But if you look at places where fluoride has been added to water for public health reasons, this relationship with IQ completely disappears, or even reverses. For example, this prospective study conducted in New Zealand looked at what happened after water was fluoridated and found no relationship between living in an area with added fluoride and IQ. The systematic review I pointed out before looked at 8 similar studies of areas where water was intentionally fluoridated, and found no relationship at all between IQ and marginally higher levels of fluorine in the water.
The other health concern that people sometimes raise is thyroid function, because there are some concerns that fluoride can impact children’s thyroid development. While there is less evidence around this point - it just hasn’t been investigated as much as the IQ concern - the studies that have been done are quite reassuring. A 2017 Canadian study showed no relationship between fluoride intake. An Indian study from 2019 similarly showed no such relationship (although it wasn’t as good as the Canadian one). A recent systematic review found no consistent relationship with fluoride in water and thyroid function, although at higher levels that you find in the natural sources (about 3x the amount we put in tap water) there was some suggestion of an increase in issues.
Overall, the evidence is quite clear . There are no consistent associations between fluoride at the levels we use for public health - about 0.5 milligrams per liter of water - and poor health. Even at the higher naturally-occurring rates, the evidence isn’t strong that fluoride can cause problems, but certainly at the incredibly low levels used to prevent dental decay there are no issues that we can find.
The benefits, however, are quite impressive. The CDC has estimated that every dollar invested into water fluoridation saves about twenty dollars in dental costs. Numerous studies over decades have shown that tiny amounts of fluoride in our water prevents a very large burden of dental issues.
Water fluoridation will probably always be controversial, because anything that the government does for the benefit of citizens will be viewed with suspicion by some people. But from a scientific viewpoint, there’s no doubt that tiny quantities of fluoride added to drinking water (or salt) are beneficial for all of us in the long run, no matter what the conspiracy theorists say.